Age
-Younger age associated with increased risk of fatal accidents. (1)
-The age group >40 have experienced rapidly increasing fatality rate since 1997. (4)

Location
-More people are killed in motorcycle crashes on rural roads than 20 years ago. Additionally, half of all crashes are on rural roads. (2)

Helmet use
-A Cochrane Review demonstrated up to 69% decrease in odds of death with helmet use. Additionally, some studies have shown no effect on neck injuries and a protective effect on facial injuries. (7)
-45% of fatally injured motorcycle riders did not wear helmets. (4)

Mandatory Helmet Laws
-68% of motorcyclists in states requiring helmet use wore DOT compliant helmets in 2006, compared to 37% in states not requiring helmets. (4).

Alcohol/Drug Abuse
-Motorcycle riders who have imbibed alcohol are more likely to lose control of their motorcycle than nondrinking riders. (1)
-49% of motorcycle crash deaths in US police reports were attributed to alcohol use, compared to 26% in other motor vehicle crash deaths. (1)
-More than 60% of all motorcycle deaths with young riders (15-29 years old) involved alcohol. (1)
-Among fatally injured young riders, one third used a combination of alcohol, and other drugs like cannabis, benzodiazepines or cocaine (1).
-32% of motorcycle riders treated in a Maryland trauma center from 1990-1991 had used cannabis prior to the crash, compared to 2.7% in car drivers. (1)

Riding speed
-Higher speeds are associated with more serious injuries. (1)
-When crash speeds exceed 50 kph, there is a reduction in helmet effectiveness in preventing death. (1)
-Speeding in fatal motorcycle crashes occurs at twice the rate for motorcycle riders compared to drivers of cars or light trucks. (1)
-Speeding is considered to be responsible for almost 2/3 of the motorcycle deaths in single vehicle crashes. (1)
-In addition to excessive speed, inappropriately slow speed for traffic conditions is associated with high risk of two-vehicle collisions. (1)

Risk taking behaviors
-Risk taking behaviors like speeding, drinking while riding, not using a helmet while riding, unlicensed riding, running yellow lights, and driving with too little headway are all thought to be risk factors for injury and death, and also appear to be correlated with each other. (1)

Lack of motorcycle licensure
-Associated with higher risk of crashing as well as with serious motorcycle injury (1).
- Among fatally injured riders, 75% had a valid license, with lowest license rate in the below 20 age group (1).

Riding a motorcycle that is not owned by the user
-Those that borrowed a motorcycle were more likely to have a crash at night, to crash while attempting a turn, or commiting a traffic violation (1).

Lack of conspicuous lights/riding wear
-2/3 of care drivers claimed not to have seen the motorcycle or saw it too late to avoid a collision. (1)
-High visibility clothing and white helmets have been shown to reduce risk of crash compared to other methods. (1)
-Use of high or low beam headlights during the day appears to be helpful. (1)

Night riding
-Almost 60% of all single vehicle crashes occur at night (2)

Size of motorcycle ridden
-41% of motorcycle fatalities occurred in 500-1000 cc category and 38% in 1000-1500 cc category. (4)
-There were increases in all engine size categories from 1997 to 2006, but the largest increase was in 1000-1500 cc. (4)